1. Field of the Invention
The present invention relates to a method for controlling a delay tolerant access of a Machine-Type Communication (MTC) device in a 3rd Generation Partnership Project (3GPP) system. More particularly, the present invention relates to a backoff method for reducing wireless network overload caused by simultaneous attempts of a plurality of MTC devices within a cell.
2. Description of the Related Art
Mobile communication systems have been developed to provide subscribers with voice communication services on the move. With the advancement of technology, the mobile communication systems have been evolved to support high speed data communication services as well as standard voice communication services. Recently, a next generation mobile communication system shifts its paradigm from Human to Human (H2H) to Machine to Machine (M2M). In order to meet this paradigm shift, the 3GPP has standardized the MTC.
The MTC has unique features as compared to normal wireless communication. The features are variously categorized according to a purpose of the MTC. For example, some MTC devices require only a few communication sessions per data regardless of time, and thus communication time has a delay-tolerant feature. Other MTC devices, installed at a fixed place to collect and transmit information without mobility, have a low mobility feature. A mobile carrier has to provide service in consideration of a coexistence between both the MTC device as well as a legacy User Equipment (UE).
A plurality of MTC devices may operate in one cell. Accordingly, when multiple MTC devices attempt to simultaneously access a network, the access may instantly cause an abrupt increase of a radio network load. Such an abrupt increase makes the radio network instable which results in an initial attachment failure of most MTC devices. Since most of the MTC devices are characterized by the delay-tolerant feature, it is not inevitable to establish a connection with a base station (evolved Node B or eNB) immediately. If the network load exceeds a preset threshold, the eNB restricts the MTC devices' initial access to the network first in order to control the overload. Recently, a method for extending an access barring mechanism has been introduced to control the network load. A normal access barring mechanism operates by transmitting related information in a System Information Block (SIB).
However, it takes a relatively long time for the eNB to acquire the SIB after its modification in structure. Accordingly, it is not efficient to adopt the normal access barring mechanism, without modification, to the wireless network in which traffic load increases abruptly.
Therefore, a need exists for a system and method for reducing a network load.